phpunit: Rename package test classes for PHPUnit 11 compat (pt 2) (#42128)

PHPUnit 10+ requires that test class names match the filename, PSR-4
style. This PR renames the test classes and files in packages to end in
`Test` or `_Test`, depending on whether the class names are following
WordPress's underscore-naming convention or are using CamelCase, and
removing redundant `WP_Test_` or `Test_` prefixes.

This also adds our standard Jetpack-Tests ruleset to
tests/.phpcs.dir.xml in the packages, and removes some redundant inline
phpcs:ignore or phpcs:disable directives.

Committed via a GitHub action: https://github.com/Automattic/jetpack/actions/runs/13637625724

Upstream-Ref: Automattic/jetpack@f1afaaa

Author: anomiex

composer.json

@@ -10,7 +10,7 @@
 		"automattic/jetpack-connection": "^6.7.0-alpha",
 		"automattic/jetpack-logo": "^3.0.2-alpha",
 		"automattic/jetpack-status": "^5.0.5-alpha",
-		"automattic/jetpack-sync": "^4.8.2"
+		"automattic/jetpack-sync": "^4.8.3-alpha"
 	},
 	"require-dev": {
 		"yoast/phpunit-polyfills": "^1.1.1",